Reactivation of paraffin alkylation catalysts



Se t. 26, 1961 P. J. LUCCHESI 3,002,038

RIF-ACTIVATION OF PARAFF IN ALKYLATION CATALYSTS Filed July 28, 1959 27 gl? II v I I0 I3 REACTION ,ZONE A Ib 29 I60 8 AIBI' PICK-UP VESSEL V 5 INITIAL SEPARATION II ZONE ISL. I8

22 A A T 3 2s HI 26 PRODUCT SEPARATION ZONE Peter J. Lucchesi INVENTOR PATENT ATTORNEY Unite States Filed July 28, 1959, Ser. No. 830,053 7 Claims. (Cl. 260-68353) This invention concerns an improved process for simultaneous cracking, isomerization and alkylation reactions wherein certain paraflin hydrocarbons are alkylated with other parafiin hydrocarbons to form branched chain paraflin hydrocarbons. The process therefore is termeda paraflin alkylation process. More specifically, the invention relates to a process wherein a butane, pentane or both are reacted with a paraffin hydrocarbon of from 6 to 18 carbon atoms in the presence of aluminum bromide and an unsaturated compound, such as maleic anhydride or acrolein, under conditions that result in high yields of branched chain paraffin hydrocarbons of from to 7 carbon atoms. The term unsaturated compound as used herein refers to an organic compound which (1) contains a CX group, where X is an electro-negative element or group and (2) has a double or triple bond carbon linkage in the alpha-beta position relative to the CX group.

The petroleum industry has been confronted with the problem of supplying sufficient quantities of high octane motor fuels which satisfy the demand of modern high compression internal combustion engines. Recently it has been found that good yields of C to C branched chain saturated paraffin hydrocarbons of high rating can be obtained by direct reaction of butanes, pentanes or isobutanes with higher paraflin hydrocarbons of from 6 to 18 carbon chain lengths in the presence of an aluminum bromide catalyst. However, in such processes the aluminum bromide catalyst has been found to be rapidly deactivated and the system therefore required frequent replenishment of the deactivated aluminum bromide. Deactivation of the catalyst is even more pronounced when the paraflin alkylation process is conducted in the vapor phase.

In accordance with the present invention it has been found that highly conjugated cyclic dienes, which are formed in the paraffin alkylation reaction, are the poisons which degenerate the catalytic activity of the aluminum bromide. It has additionally been discovered, however, that these continually forming poisons may be counteracted by conducting the paraflin alkylation reaction in the presence of an unsaturated compound which reacts With the dienes to form promoters. To achieve these ends a variety of methods are available. For example, the unsaturated compound may be added to any one or more of the feed streams, directly into the reaction zone, or to both the feed stream and the reaction zone.

The nature and objects of this invention and the manner in which the invention can be practiced will be more readily understood from the foregoing detailed description of the process. Reference Will be made to the accompanying drawing in which the single figure is a schematic flow plan of one process for practicing the instant invention.

The process Will be described with particular reference to the use of isobutane as the lighter component, the AlBr catalyst supported on or associated with gamma alumina and the feeds containing surplus AlBr Referring to the drawing in detail, a suitable butane feed stream containing, at least initially, a major proportion of isobutane is obtained by means of line 11 from a suitable source. A portion of the stream is conducted via line 11a through an aluminum bromide pick-up vessel 12 to dissolve aluminum bromide in a portion of the stream that is conatent C ice ducted to the reaction zone. The remainder of the feed stream is combined with the effluent leaving the pickup vessel via line 13 and is conducted into a reaction zone 15. The latter zone contains one or more beds of gamma alumina saturated with aluminum bromide.

A stream of a higher paraflin hydrocarbon, as for example heptane, octane, dodecane or cetane, or a mixture containing the higher paraflins, is conducted into the reaction zone by means of line 16. Preferably the stream enters the reaction zone at a plurality of spaced points, 16a, 16b, etc., so as to insure as high a ratio as possible of isobutane to higher parafin at any particular point in the reaction zone.

The unsaturated compound is added to the system at any one of a number of places, for example, through line 27 which connects to the butane feed line 11, through line 28 which connects with the higher paraflin feed line 16, or through line 29 which directly communicates with the reaction zone 15, in amounts below 2 wt. percent based on the total feed rate or below 6 wt. percent based on the higher paraffin feed rate. The unsaturated compound reacts with the highly conjugated cyclic dienes in a manner similar to a Diels-Alder reaction and converts the diene poison to a compound having promoter characteristics because of its available active group. Thus the addition of malcic anhydride, for example, causes the following reaction to occur:

0 0 11 0/ o l c I /C /O C CI1 /O C-C H 0 ll j 0 Diane poison Maleic anhydride Promoter In the liquid phase parafiin alkylation process the unsaturated compound is selected so that it may be added to the process in liquid phase. When the paraifin alkylation process is conducted in the vapor phase an unsaturated compound is selected which has a boiling point such that it may be added to said process in vapor phase. It is material only that the unsaturated compound be present in the reaction zone in sufficient quantity to coun teract the dienes being formed and the method by which it is so directed to said reaction zone is immaterial in the instant application.

The paraflin alkylation reaction product leaves the reaction zone through line 18 and is conducted into an initial separation zone 20 wherein light materials, including unreacted isobutane and normal butane, are removed overhead and recycled to the reaction zone by means of line 21. The heavier material, including C hydrocarbons and higher, is conducted by means of line 22 into a product separation zone 24 wherein C to C hydrocarbons are removed overhead by means of line 25 while heavier material comprising C hydrocarbons and higher as well as any aluminum bromide that has been removed from the reaction zone is recycled to the reaction zone by means of line 26. If desired, conditions can be adjusted in separation zone 24 to include normal heptane in the heavier material recycled through line 26, While including the C branched chain isomers in overhead line 25.

In place of isobutane the feed in line 11 may comprise normal butane, in which case no higher hydrocarbon feed stock will be sent initially to the reaction zone but the butane will be recycled through line 18, zone 20 and line 21 until a considerable amount of the butane has been isomerized to isobutane. The process may then continue in the manner already described, the recycle isobutane being sufiicient to make the desired reaction proceed .while 3 the fresh butane feed becomes isomerized to isobutane in the reactor.

Temperatures in the range of from about 30 F. to about 140 F. and pressures sufiicient to keep the materials in liquid phase are employed in the above-described process. It is critical in the above-described process that the temperature be maintained below about 140 F. to obtain proper distribution of the products. At temperatures above about 140 F. considerable cracking occurs and the principal products are propane and lighter materials.

Although the reaction may proceed in the absence of a hydrogen bromide promoter it is preferred that it be used as an auxiliary promoter in addition to the gamma alumina. A range of from about 0.1 to 8% or more of HBr by weight based on total feed may be used, while about 1% to about is preferred. The hydrogen bromide is introduced into the reaction zone by means of line 17 and is recycled to the reaction zone along with unreacted butanes by means of line' 21.

It is preferred that the minimum mol ratio of isobutane and/or isopentane to higher parafiin be about 3 to 1 but should preferably be no higher than about 12 to 1. The feed stock should be essentially free of aromatics. Feed rates may vary from about 0.3 to about 2 v./hr./v. (liquid volume of total feed per hour per volume of total catalyst plus support).

Although the detailed description has been limited to an aluminum bromide catalyst supported on gamma alumina such is merely for illustrative purposes. The present invention may be employed in a process wherein the aluminum bromide catalyst is supported by Porocel, employed in the presence of a hydrogen halide promoter such as hydrogen bromide, unsupported or any combination thereof. A mixed catalyst in which a portion of the aluminum bromide is replaced with aluminum chloride may also be used.

Furthermore, although the process as described in conjunction with the drawing contemplates downflow of the stream through the catalyst bed, upflow can also be used. In place of a fixed bed process, a moving bed of catalyst could be used. Alternatively, a slurry type of operation could be employed wherein a suspension of catalyst is maintained in the reacting hydrocarbons, the slurry being stirred in the reactor with suitable mechanical stirring means or recirculated through the reactor by pumping means. Here again the unsaturated compound may be added to any feed stream or directly to the slurry in the reactor. Where slurry operation is used, the slurry is removed from the reactor at the end of the reaction period, in case of batch operation, or as a fraction of the circulating stream in the case of continuous operation, and sent to suitable separation equipment to separate the catalyst from the hydrocarbons. The preparation equipment may comprise a simple settling tank, a centrifuge, or a filter, for example, or suit able combination of such means.

To remove aromatics from the feed stock conventional techniques may be employed such as solvent extraction, hydrogenation, acid treating and the like, as well as treatment with selective adsorbents such as molecular sieve zeolites. It is not necessary that the higher hydrocarbons used be individual hydrocarbons such as heptane or octane or cetane, for example, but mixtures may be used, such as a petroleum fraction containing parafl'inic hydrocarbons in the range of 6 to 18 carbon atoms. Although, as stated, hexane is one of the higher hydrocarbons that may be used, it is preferred to employ heptane or higher. Essentially the same product distribution is obtained with hexane as with heptane but the reaction rate is lower by a factor of about 3. Other sources of the higher paraffin hydrocarbons for the reaction include light virgin naphthas, and parafiin rafiinates from the extraction of hydroformed petroleum fractions.

If the aluminum bromide is to be supported by gamma alumina, the latter may be saturated with aluminum bromide and then placed in the reaction zone, or, alternatively, it may be placed alone in the reaction zone and then saturated with aluminum bromide carried in with a portion of the feed. Another method for the preparation for this catalyst is to mix the aluminum halide with the support and heat the mixture to efiect impregnation. If desired, loosely held aluminum halide may be removed from the catalyst mass by heating the mass and passing through it a gas such a carbon dioxide, methane, hydrogen or nitrogen.

Alternatively the support may be impregnated by dissolving the aluminum halide in a suitable solvent such as ethylene dichloride or dioxane, for example, and the porous carrier impregnated with this solution, followed by heating to remove the solvent and loosely held aluminum halide. Still another alternative is to employ a powdered support or promoter, mix the aluminum halide with it, and compress the mixture into pellets.

The preferred embodiment of this invention resides in the use of the unsaturated compound in a vapor phase paraffin alkylation process wherein it has been found that the AlBr catalyst is more active, but, on the other hand, is poisoned more rapidly than in a liquid phase parafiin alkylation process. The need for the regenerating characteristics of the unsaturated compounds is therefore substantially increased. The vapor phase processes may be operated in the same manner disclosed for the various liquid phase processes, the only dilferenccs being that the feed, reaction products, and additional components are maintained in vapor phase. The vapor phase paratfin alkylation processes may be carried out within the temperature range of from about F. to about 400 F. SuflEicient pressure is maintained to prevent condensation of the feeds, reaction products and additional components. The unsaturated compound employed herein has a boiling point such that it may be added in vapor phase to the feed or directly to the reaction zone. Hydrogen may also be added in the vapor phase operation.

The effect of the dienes formed in the paraftin alkylation process and of the addition of an unsaturated compound is vividly exemplified by the following test. A catalyst comprising AlBr (23 gms.) on a Porocel support (46 gms.) was used as the standard for paraffin alkylation activity of 100%. Five samples of the Porocel supported aluminum bromide were used and their activity compared after a diene alone or a diene and maleic anhydride had been added to said catalyst. The diene added to the catalyst was the actual poison previously separated from spent paraffin alkylation catalysts. It was shown to be a substituted cyclopentadiene derivative. The results are shown in Table A below:

TABLE A Relative catalytic activity of parayfin alkylation catalyst in the presence of dienes and maleic anhydride Catalyst, AlBra/Porocel, gms 70. 8 70. 8 70. 8 70.8 70.8 Diene added, grns 0 2. 4 3.0 2. 4 3.0 Maleic Anhydride added, gms 0 0 0 3.1 3. 5 Relative Catalyst Activity 100 48 2E) 75 85 The relative catalyst activity was determined by a standard batch stirred-reactor experiment in which ml. isobutane, 38 ml. n-heptane, and 2 ml. methylcyclohexane are reacted at 72 F. for 3 hours over a catalyst comprising 23.6 gm. AlBr on 47.2 gm. Porocel support. The catalyst activity is measured by the conversion (which follows a first order law with regard to n-C concentration) at the end of this period and provided the basis of comparison. The conversion obtained in the above procedure by the catalysts which had added thereto the diene alone or the diene and maleic anhydride were compared to the conversion of the standard AlBr Porocel catalyst to determine the relative catalyst activity.

It may be seen from the above tests that the diene decidedly reduced the catalytic activity of the AlBr /Porocel catalyst and that the addition of the maleic anhydride almost fully counteracted this detrimental efiect.

Although this invention has been discussed primarily in relation to the use of maleic anhydride, as previously mentioned any organic compound which (1) contains a CX group, where X is an electro-negative element or group and (2) has a double or triple bond carbon linkage in the alpha-beta position relative to the CX group would be equally applicable. Illustrative of electronegative elements and groups are CN, 0, halogen, NCS, NH N However, the preferred unsaturated compounds for use in the instant process are those which contain a 0:0 group and have a double bond carbon linkage in the alpha-beta position relative to the C O group. Such compounds are more commonly referred to as alpha-beta unsaturated carbonyls and maleic anhydride, the most preferred single compound, would be illustrative of these carbony-ls. The following class of organic compounds exemplify the materials which are represented by the term unsaturated compounds employed herein:

What is claimed is:

l. A process for the preparation of high octane naphtha components consisting largely of branched chain paraflin hydrocarbons of to 7 carbon atoms which comprises reacting in liquid phase a minor proportion of a straight chain paraflin hydrocarbon of from 6 to 18 carbon atoms with a major portion of a lighter hydrocarbon selected :from the group consisting of butanes and pentanes, at temperatures no higher than about 140 F., in a reaction zone in the presence of an aluminum bromide catalyst and maleic anhydride.

2. A process as defined in claim 1 wherein the aluminum bromide is supported by gamma alumina.

3. A process as defined in claim 1 wherein said maleic anhydride is mixed with the straight chain parafiin hydrocarbon of from 6 to 18 carbon atoms prior to said hydrocarbon reacting with the lighter hydrocarbon selected from the group consisting of butanes and pentanes.

4. A process as defined in claim 1 wherein said maleic anhydride is added to the process in amounts below about 2 wt. percent total feed to the reaction zone.

5. A process for the preparation of high octane naphtha components consisting largely of branched chain paraffin hydrocarbons of 5 to 7 carbon atoms which comprises reacting in vapor phase a minor proportion of a straight chain paraffin hydrocarbon of from 6 to 18 carbon atoms with a major portion of a lighter hydrocarbon selected from the group consisting of butanes and pentanes, at temperatures within the range of from about F. to about 400 F. in a reaction zone in the presence of an aluminum bromide catalyst and maleic anhydride.

6. A process as defined in claim 5 wherein said maleic anhydride is added to the process in amounts below about 2 wt. percent total -feed to the reaction zone.

7. A process as defined in claim 5 wherein said maleic anhydride is mixed with the straight chain paraffin hydro carbon of from 6 to 18 carbon atoms prior to said hydrocarbon reacting with the lighter hydrocarbon selected from the group consisting of butanes and pentanes.

References Cited in the file of this patent UNITED STATES PATENTS 2,220,090 Evering et al. Nov. 5, 1940 7 2,349,458 Owen et al. May 23, 1944 2,422,798 Pines June 24, 1947 

1. A PROCESS FOR THE PREPARATION OF HIGH OCTANE NAPHTHA COMPONENTS CONSISTING LARGELY OF BRANCHED CHAIN PARAFFIN HYDROCARBONS OF 5 TO 7 CARBON ATOMS WHICH COMPRISES REACTING IN LIQUID PHASE A MINOR PROPORTION OF A STRAIGHT CHAIN PARAFFIN HYDROCARBON OF FROM 6 TO 18 CARBON ATOMS WITH A MAJOR PORTION OF A LIGHTER HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BUTANES AND PENTANES, AT TEMPERATURES NO HIGHER THAN ABOUT 140*F., IN A REACTION ZONE IN THE PRESENCE OF AN ALUMINUM BROMIDE CATALYST AND MALEIC ANHYDRIDE. 